GCN Circular 42007
Subject
GRB 250925A: Swift/UVOT Upper Limits
Event
Date
2025-09-26T16:33:59Z (7 days ago)
From
noelklin@umbc.edu
Via
Web form
N. J. Klingler (NASA-GSFC/UMBC/CRESST II) reports on behalf of the
Swift-UVOT team:
Swift-UVOT has performed follow-up observations of the Swift-BAT-detected burst GRB 250925A (Dichiara et al. GCN 41985), collecting 6.0 ks of observations between T0+3.74 ks and T0+16.74 ks. No source was detected in the UVOT data at the position of the optical source detected by the Nordic Optical Telescope (NOT) reported by Corcoran et al. (GCN 41990; RA, Dec = 22 44 51.31, +46 33 21.3), which is also consistent with the enhanced position of the X-ray source detected by Swift-XRT reported by Page et al. (GCN 41988; RA, Dec = 22 44 51.30, +46 33 20.6).
3-sigma upper limits (AB) using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 4150.3 4350.1 199.80 >21.55
white 9527.3 10434.5 907.20 >22.41
B 3945.3 5554.0 1608.70 >21.16
U 3739.8 3939.6 199.80 >20.48
U 5175.9 5375.7 199.80 >20.52
V 4560.9 4760.7 199.80 >19.94
V 15320.0 16227.1 907.10 >20.81
W1 4971.0 5170.7 199.70 >20.10
W2 4356.1 4555.9 199.80 >20.10
W2 10440.9 11158.4 717.50 >21.02
M2 4765.8 4965.6 199.80 >19.99
M2 16232.4 16737.3 504.90 >20.67
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.254 in the direction of the burst (Schlegel et al. 1998).